Summary of Work: This project will explore the complexity of mismatch repair in higher cells. Specifically, we are interested in elucidating the roles of MSH4 and MSH5 in recombination and any possible redundancy in DNA repair. Studies from Ross-Macdonald and others have shown that MSH4 expression is highest during early meiosis and is not detectable during vegetative growth. Hence, both MSH4,5 appear to have no role in the repair of DNA biosynthetic errors during replication. Current models of recombination and mismatch repair suggest that branch migration is mediated by mismatch repair when markers are selected in the vicinity of sequence divergence. In addition, recent studies have implicated MSH2 in facilitating DNA crossovers. We would like to established in more detail the role(s) of MSH4 and MSH5 in both mitosis and meiosis. Currently we have amplified out Saccharomyces cerevisiae MSH4 from the chromosomal DNA along with obtaining the MSH5 plasmid. MSH5 has been fused to the gal 10 promoter so as to allow coexpression of both MSH4 & MSH5. - Biochemistry, Crossing Over(Genetics), DNA- Binding Proteins, DNA Repair, Mutation, Recombination, Genetic Sister Chromatid Exchange